CorexoTools

Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals back to numbers.

Number to Roman

MMXXVI

Roman to Number

2026

What is a Roman Numeral Converter?

A Roman numeral converter translates between the everyday Arabic numbers we calculate with (1, 2, 3 …) and the Roman system of letters (I, V, X, L, C, D, M) inherited from ancient Rome. The Roman system has no zero and no place value — instead it builds numbers by adding and subtracting letter values. Converting by hand is error-prone, so this tool does it both ways: type a number to get its Roman form, or type a Roman numeral to get the number it represents.

The seven symbols carry fixed values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. Numbers are written from largest to smallest, left to right, and the values are added — so MMXXIV is 1000 + 1000 + 10 + 10 + 4 = 2024.

How to Use the Converter

  1. To convert a number to Roman: type a value between 1 and 3999 into the number field.
  2. To convert a Roman numeral to a number: type letters such as XLII into the Roman field.
  3. The result appears instantly — there is no button to press.
  4. Invalid input (such as a number outside the range, or a malformed numeral) is flagged rather than silently producing a wrong answer.
  5. Copy the result and use it in dates, titles, page numbers, or wherever you need it.

Subtractive Notation and the 1–3999 Range

The key rule that trips people up is subtractive notation. Rather than writing four identical symbols, Roman numerals place a smaller symbol before a larger one to mean “subtract.” So 4 is IV (one before five), not IIII; 9 is IX; 40 is XL; 90 is XC; 400 is CD; and 900 is CM. Only these six subtractive pairs are valid — you cannot, for example, write IC for 99 (the correct form is XCIX).

This converter covers the standard modern range of 1 to 3999. There is a practical reason: the largest single symbol is M (1000), and Roman convention does not repeat a symbol more than three times, so the highest cleanly writable value is MMMCMXCIX= 3999. Larger numbers historically used a bar over a symbol to multiply it by 1000, but that notation is rarely needed today. Roman numerals still appear on clock faces, in book chapter numbers, in movie copyright years, on building cornerstones, and in the names of monarchs and popes — which is exactly where a quick converter saves time.

Frequently Asked Questions

Why can't I convert 0 or negative numbers?

The Roman system has no symbol for zero and no concept of negative numbers. The converter therefore accepts only positive integers from 1 upward.

Why is IIII rejected for 4?

Standard Roman numerals never repeat a symbol four times. The canonical form of 4 is IV. The clock-face style IIII is a decorative exception, not valid notation, so the converter expects IV.

What is the largest number I can convert?

3999, written MMMCMXCIX. Standard notation cannot cleanly express larger values without the bar-multiplier convention, which this tool does not use.

Does the converter need an internet connection to work?

No. The conversion logic runs entirely in your browser. Once the page has loaded, nothing is sent to a server and no data about your input is collected.